Method and covering fabric for a damping form roller of an offset printing machine

ABSTRACT

A cylindrical fabric covering of a larger diameter than a form roller of an offset printing machine contains a water shrinkable ground yarn and a hydrophilic pile yarn. The pile yarn can be cut to the desired size and the cylindrical fabric is securely fastened to the form roller by submerging the cylindrical fabric and roller in water until the fabric shrinks firmly on the roller. The resulting firmly fixed fabric covering largely eliminates the generation of lint or fluff with its resulting effects on the prints.

United States Patent [1 1 1111 3, Nishiwaki [451 Dec. 16, 1975 METHOD AND COVERING FABRIC FOR A 2,312.353 3/1943 Toland 29/131 DAMPING FORM RQLLER O AN OFFSET 2,345,337 3/1944 Gardner 29/120 2.775.195 12/1956 Martin 1. 29/120 X PRINTING MACHINE 2.801762 9/1957 Kumeda 29/120 X [75] Inventor: Hiroshi Nishiwaki, Osaka, Japan 3.180.115 4/]965 Marshall 29/l20 X i 2 [73] Assignees: Unitika Ltd., Amagasaki; Katsura 3'242'5'4 Raimond 29/1 0 Roller Mfg, C Ltd O k b FOREIGN PATENTS OR APPLICATIONS of p n 404.051 H1934 United Kingdom 29/131 22 F1 d: Se 1. 26, 1 7 l 1 p 9 3 Primary ExaminerMar1on E. McCamtsh 1 1 PP 4001991 Attorney, Agent, or Firm-Sughrue, Rothwell, Mion,

Related US. Application Data Zmn & Macpeak [63] Continuation-impart of Serr No. 143,607, May 14.

1971, abandoned. [57] ABSTRACT A cylindrical fabric covering of a larger diameter than [52] US. Cl. 156/86; 29/ I20; 29/ 131; a f rm roller of an offse prin ing m hine ontain 3 29/132; 66/194; 66/198; 428/36; 428/95 water shrinkable ground yarn and a hydrophilic pile [51] Int. Cl. B21B 31/08; 8603 7/00 yarn. The pile yam n be cut to h esired size and 581 Field of Search 29/120, 129.5, 131, 132; the cylindrical fabric is Securely fastened to the form l61/6267; 66/194, 198; 139/3855, 387 R, roller by submerging the cylindrical fabric and roller 39], 404; 428/36, 85, 92, 95; 156/84, 86 in water until the fabric shrinks firmly on the roller.

The resulting firmly fixed fabric covering largely elimi- [56] References Cited nates the generation of lint or fluff with its resulting UNITED STATES PATENTS effects the P l,281.940 10/1918 Goedilte 29/131 2 Claims, 5 Drawing Figures U.S. Patent Dec. 16, 1975 3,926,701

METHOD AND COVERING FABRIC FOR A DAMPING FORM ROLLER OF AN OFFSET PRINTING MACHINE CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 143,607, filed May 14, 1971, and now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved cover ing fabric to form the outer surface of a damping form roller on a plate cylinder of an offset printing machine for supplying water to the plate cylinder. More particularly, the invention relates to a covering fabric for a damping form roller for an offset printing machine prepared by knitting or weaving fibers shrinkable by water as ground yarns and hydrophilic fibers as pile yarns. Either yarn may be either the warp yarn or the weft yarn.

The covering fabric of this invention can be readily fitted on a damping form roller and can supply water to the plate cylinder in a smooth and uniform manner, thereby aiding in producing fine and beautiful prints continuously for a long period of time.

2. Description of the Prior Art In offset printing it is necessary to supply water to the plate cylinder of an offset machine, and this water supply is an important factor in determining the finishing of prints. Hitherto, the most popular damping form roller covering fabrics, used to supply water to the plate cylinder, were prepared by fabricating a cloth made by knitting or weaving cotton into a cylindrical shape, mounting it onto a damping form roller, and stretching it by pulling the opposite ends of the cylindrically shaped cloth before use. However, this conventional technique is accompanied with difficulties in that the covering fabric is apt to be loosened by the centrifugal force during rotary use of it, the supply of water to the plate cylinder becomes uneven due to uneven stretching, fluff is generated, and cutting takes place which results in reducing the printing preciseness. The printing operation must, therefore, be interrupted frequently to replace the covering fabric with a fresh one or to rebind the old one, which results in reducing the efficiency of the printing operation. Also, the replacing operation of the covering fabric is quite troublesome and requires expensive skilled labor.

US. Pat. No. 3,242,554, issued on Mar. 29, I966, discloses damping roller covers made from watershrinkable fabrics. With these fabrics, the damping rol- Ier is inserted in a cylindrical cover, the assembly is immersed in water, and the cover is shrunk on the roller. However, the particular water-shrinkable fabrics disclosed in that patent must first be wet-stretched and then dried prior to use, and they stretch to only a very limited degree, in the vicinity of 5%, and then shrink by less than the original stretching when wetted, This limited shrinking means that the covers must be very carefully measured to the rollers on which they are to be used and that the same size covers cannot be used on rollers after they are reground, as they must be periodically during use.

SUMMARY OF THE INVENTION The present invention has succeeded in obtaining an excellent covering fabric for a damping form roller without the accompanying difficulties experienced by either the conventional stretched covers or by the prior art water-shrinkable covers.

The object of this invention is to provide a covering fabric for a damping form roller which can be mounted on the damping form roller quite readily, can be brought into contact with the roller closely and uniformly, can supply water to the plate cylinder uniformly and smoothly, forms no fluff, and is adapted for use with damping rollers varying significantly in diameter.

One of the yarns composing the covering fabric of this invention is required to be composed of fibers that are capable of shrinking by the action of water or warm water. Such fibers having the properties mentioned above, are prepared by spinning polyvinyl alcohol, par tially acetylated polyvinyl alcohol. partially acetalized polyvinyl alcohol, partially kctalized polyvinyl alcohol, partially carbamated polyvinyl alcohol, or a mixture of a main proportion of polyvinyl alcohol and a small proportion of such polymer as polyethylene. polyacryloni triI or polyvinyl chloride by a wet system. a dry system. a dry system or a semi-melt spinning system and stretching and drying the fibers. To obtain best results, non acetalized fibers are used, and the fibers thus prepared are heat treated lightly. A highly stretched, high tenacity fiber, such as rayon fibers may be employed in this invention. The form of the fibers used in this invention may be either filament or spun yarn.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I shows a damping form roller covered by a cover made in accordance with the present invention.

FIG. 2 shows the fabric of the present invention in its slackened state, before getting wet.

FIG. 3 shows the ground yarns used in the present invention.

FIG. 4 shows the pile yarns used in the present invention.

FIG. 5 shows the fabric of the present invention in its shrunk state, after getting wet.

DESCRIPTION OF THE PREFERRED EMBODMIENT The present invention provides a cover for a damping form roller prepared by knitting or weaving fabric into a cylindrical form. One such cover I0 mounted on a damping form roller 12 is shown in FIG. 1. Some of the fibers of the cylindrical form have the propery of being capable of shrinking due to the action of water. Other fibers of the cylindrical form are selected from one or more hydrophilic fibers selected, for examle, from vegetable fibers such as cotton and hemp; animal fibers such as wool and silk; regenerated fibers such as viscose rayon and cuprammonium rayon; and vinylon. It is also possible to produce the covering fabric of this invention by cutting the fabric thus knitted or woven and sewing the fabric into a cylindrical shape. In the case of a pile-shaped knitted or woven product, the fibers having the capacity to shrink by the action of water are used as the ground yarn of the covering fabric, and the hydrophilic fibers are used as the pile yarn. In other forms of a covering fabric, the fibers having the capacity to shrink in water are used as either the weft or the 3 warp, and the hydrophilic fibers are employed respectively as the warp or the weft.

Where the fabric is subjected to a napping treatment, the yarns composed of the hydrophilic fibers are napped. That is, the fibers having the property of shrinking with water are employed as the ground yarns or the wefts or warps and the hydrophilic fibers are employed as the pile yarns. or respectively the warps or wefts.

A fabric illustrating the above principles is shown in FIGS. 2-5, wherein a PVA multi-filament fiber l4 having a shrinkable nature is used as the ground yarn and a hydrophilic yarn 16 (shown as napped in FIG. 4) is used as the pile yarn.

in mounting the covering fabric of this invention on a damping form roller, the roller with the covering fabric is generally immersed in water, often warm water, and the ground yarns or the wefts or warps of the covering fabric shrink to closely fix the covering fabric to the surface of the damping form roller. By this method, the pile yarns or the warps or wefts respectively composed of the hydrophilic fibers are firmly fixed to the roller by the above-mentioned shrunken yarns, which thereby prevents the fonnation and falling of fluff.

Thus, by the present invention, the covering fabric of the damping form roller can supply in a smooth and uniform manner water to the plate cylinder by virtue of the good water absorbing property of the fabric while not permitting the covering fabric to loosen from the damping form roller and therby permit a printing of high quality to be conducted continuously for a long period of time.

in order to realize the above-mentioned advantages concerning use with rollers of varying size, the shrinkable fibers used are preferred to be capable of shrinking more than 5%. Generally in cases of fibers consisting of mainly polyvinyl alcohol, the shrinkage percentile is between -40%. When rayon fibers of a high stretch, high tenacity capability are immersed in water, they generally shrink by about 10% and are quite capable of use as yarns of the covering fabric of the present invention, although of course they do not provide as much flexibility as PVA fibers do.

When the covering fabric has a longer length than the damping form roller, the shrinking of the fabric upon the roller will fix the fabric both on the roller surface and at the ends of the roller which further strengthens the connection of the fabric with the roller.

To aid in understanding the present invention, the following Examples are set forth, although it should be realized that the present invention should not be limited to these examples:

EXAMPLE l A cylindrical knitted pile fabric having piles 5 mm long was prepared by means of a circular knitting machine 4- /2 inches in diameter, employing l44 needles and sinkers. As the ground yarn, a 750 denier multifilament yarn consisting of 83 filaments of lightly heattreated and non-acetalized polyvinyl alcohol which is capable of shrinking by 27% when immersed in water for 5 minutes was used. The pile yarn was a llOO denier/500 filament ordinary rayon multifilament yarn. The piles were cut by means of a shearing machine thus producing a cylindrical fabric having a pile length of 4 mm and a fold width of 130 mm. The opposite ends of the cylindrical fabric were cut away so that each end of the fabric protuded beyond the end of a damping form roller by 50 mm when the cylindrical fabric was mounted on the roller. After the cylindrical fabric was mounted on the damping form roller, the excess end portions were affixed by means of a cord and the roller was immersed in water. The cylindrical fabric shrunk onto the roller to affix the fabric strongly and uniformly across the surface of the rubber roller. A resulting op eration with the cylindrical fabric failed to loosen the fabric during the operation. Because the covering fabric initially had an inner diameter larger than the diameter of the damping form roller, the covering fabric was readily mounted on the roller prior to the shrinking. The covering fabric of this Example was readily adaptable to rubber rollers with diameters ranging from 55 mm to 75 mm and thus had a wide usable range.

On the other hand. a covering fabric prepared by the same method as above, except that the ground yarns of the covering fabric were made of cotton yams, was only applicable to rubber rollers of a diameter range from mm to mm and the mounting of the covering fabric was difficult when compared with the abovedescribed covering fabric.

EXAMPLE 2 A cylindrical fabric was prepared by knitting llOO denier/ l lOO filament high tenacity rayon yarns which could shrink by 12% when immersed in water for more than 1 minute. The rayon yarns were used as the ground yarns and doublings of two 40 Ne cotton yarns were used as the pile yarns in the same manner as in Example l. Also the cylindrical fabric was sheared as in the same Example. When the covering fabric was mounted on the damping form roller as in Example I, and the roller was immersed in water, the ground yarns shrunk to fix tightly the covering fabric to the rubber roller, and the occurence of falling fluff was substantially less than in a conventional covering.

The covering fabric could be used for rubber rollers having a varying diameter from 55 mm to 75 mm. As a comparison a covering fabric was prepared by the same method as above, except that both the ground yarns and the pile yarns of this covering fabric was made of cotton yarns. During operation of the roller, the covering fabric loosened due to the centrifugal force and in addition,, suffered much falling of fluff. Consequently, the covering fabric was unsuitable for printing after a period of operation while the above-described fabric of the present invention was capable of further use.

EXAMPLE 3 A cylindrical fabric having a fold width of 190 mm was prepared by weaving a cylindrical form and using as the warps a filament yarn of polyvinyl alcohol as used in Example 1 as the ground yarns and 40/2 Ne rayon staple yarn as the wefts. The wefts were napped in a lengthwise direction by means of a wire napping machine followed by a shearing. The cylindirical fabric was mounted on a rubber roller having a diameter of mm and the roller was immersed in water which subsequently shrunk the cylindrical fabric tightly onto the roller. The resulting damping roller provided an ample supply of water to the plate cylinder. The cover ing fabric prepared could be applicable to rubber rollers of a diameter ranging from 80 mm to mm.

What is claimed is:

1. ln cylindrical damping form covers which are water-shrinkable over damping form rollers, the improvement wherein a damping form cover comprises S pile yarns composed of hydrophilic vegetable or regenerated fibers and ground yarns composed of lightly heat-treated and nonacetalized multifilament polyvinyl alcohol fibers, said multifilament polyvinyl alcohol fibers being capable of shrinking by 27-40% in the direction of the length thereof when moistened with water in the absence of previous stretching, whereby said damping form cover may be fixed firmly on a damping form roller or less smaller in diameter than said damping form cover due to the shrinkage of the ground yarns when the roller is inserted therein, both ends of the damping form cover are fixed with fibers, and the roller and cover are moistened.

2. A method of covering a damping form roller for an offset printing machine comprising the steps of:

6 l forming a cylindrical cover from a fabric comprismg: a. pile yarns composed of hydrophilic vegetable or regenerated fibers and b. ground yams composed of lightly heat-treated and nonacetalized multifilament polyvinyl alcohol fibers, said multifilament polyvinyl alcohol fibers being capable of shrinking by 27-40% in the direction of the length thereof when moistened with water in the absence of previous stretching; 2. inserting the roller into the cylindrical cover; and 3. wetting the roller and cylindrical fabric with water until the cylindrical fabric has shrunk sufficiently to firmly position the cylindrical fabric on the rol- 

1. FORMING A CYLINDRICAL COVER FROM A FABRIC COMPRISING: A. PILE YARNS COMPOSED OF HYDROPHILIC VEGETABLE OR REGENERATED FIBERS AND B. GROUND YARNS COMPOSED OF LIGHTLY HEAT-TREATED AND NONACETALIZED MULTIFILAMENT POLYVINYL ALCOHOL FIBERS, SAID MULTIFILAMENT POLYVINYL ALCOHOL FIBERS BEING CAPABLE OF SHRINKING BY 27-40% IN THE DIRECTION OF THE LENGTH THEREOF WHEN MOISTENED WITH WATER IN THE ABSENCE OF PREVIOUS STRETCHING;
 1. IN CYLINDRICAL DAMPING FORM COVERS WHICH ARE WATERSHRINDABLE OVER DAMPING FORM ROLLERS, THE IMPROVEMENT WHEREIN A DAMPING FORM COVER COMPRISES PILE YARNS COMPOSED OF HYDROPHILIC VEGETABLE OR REGENERATED FIBERS AND GROUND YARNS COMPOSED OF LIGHTLY HEAT-TREATED AND NONACETALIZED MULTIFILAMENT POLYVINYL ALCOHOL FIBERS, SAID MULTIFILAMENT POLYVINYL ALCOHOL FIBERS BEING CAPABLE OF SHRINKING BY 27-40% IN THE DIRECTION OF THE LENGTH THEREOF WHEN MOISTENED WITH WATER IN THE ABSENCE OF PREVIOUS STRECHING, WHEREBY SAID DAMPING FORM COVER MAY BE FIXED FIRMLY ON A DAMPING FORM ROLLER 5% OR LESS SMALLER IN DIAMETER THAN SAID DAMPING FORM COVER DUE TO THE SHRINKAGE OF THE GROUND YARNS WHEN THE ROLLER IS INSERTED THEREIN, BOTH ENDS OF THE DAMPING FORM COVER ARE FIXED WITH FIBERS, AND THE ROLLER AND COVER ARE MOISTENED.
 2. A METHOD OF COVERING A DAMPING FORM ROLLER FOR AN OFFSET PRINTING MACHINE COMPRISING THE STEPS OF:
 2. INSERTING THE ROLLER INTO THE CYLINDRICAL COVER; AND
 3. WETTING THE ROLLER AND CYLINDRICAL FABRIC WITH WATER UNTIL THE CYLINDRICAL FABRIC HAS SHRUNK SUFFICIENTLY TO FIRMLY POSITION THE CYLINDRICAL FABRIC ON THE ROLLER.
 3. wetting the roller and cylindrical fabric with water until the cylindrical fabric has shrunk sufficiently to firmly position the cylindrical fabric on the roller. 